<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let age=prompt('请输入年份')
        if(age%4==0&&age%100!=0||age%400==0){
            alert('该年份为闰年')
        }
        else{
            alert('该年份为平年')
        }
    </script>
</body>
</html>